The invention relates to a photochromic composition, and more particularly to an organic photochromic composition comprising spiro (indoline-2,3'-(3H)-napth-(2,1-b)(1,4) oxazine)(SO) dye, with substitution of a trifluoromethyl group in the indoline part of the molecule.
As used throughout this specification and claims, the terms (SO) dye, (SO) compound or (SO) derivative are intended to represent a compound having the following structural formula: ##STR1## wherein "SO" is an abbreviation for spiro (indoline-2,3'-(3H)-napth(2,1-b)(1,4) oxazine), and hereinafter the parent compound is a (SO) compound wherein R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are hydrogen.
Compounds which undergo reversible photo-induced color changes are termed photochromic compounds. When subjected to ultraviolet light or visible irradiation, these photochromic compounds change their transmission. They subsequently revert to their original color state when they are subjected to a different wavelength of radiation or when the initial light source is removed.
The photochromism of (SO) compounds was first disclosed in U.S. Pat. Nos. 3,562,172 and 3,578,602. These compounds are (SO) derivatives with substitutions in the indoline part of the molecule. Subsequently, U.S. Pat. Nos. 4,215,010 and 4,342,668 disclosed (SO) derivative compounds with substitution in the naphthalene part of the molecule in addition to substitution in the indoline part of the molecule. These (SO) derivative compounds in the two latter patents show an enhanced photocolorability when compared to the (SO) derivative compounds disclosed in U.S. Pat. Nos. 3,562,172 and 3,578,602.
A solution of all (SO) derivative compounds in common organic solvents, as disclosed in the four above-mentioned patents, is colorless or slightly blue before ultraviolet light irradiation and becomes an intense blue color after irradiation. When (SO) derivatives are incorporated into a plastic host material, such as cellulose acetate butyrate, (CAB), the resulting material shows this same photochromic behavior. A great deal of effort has been made to avoid this intense blue color. However, until the present invention, this effort has failed as evidenced by the intense blue color shown in all of the compounds disclosed in the above-mentioned patents.
It was also found that with some of the (SO) derivative compounds of the above-mentioned patents there is a large thermal equilibration toward the colored form. Thus, when these particular (SO) compounds are incorporated into a plastic host, the resulting structure exhibits a low luminous transmittance in the unactivated state (before ultraviolet light irradiation), which renders these compounds undesirable for applications such as in lenses which go from a clear to a colored form. When an ultraviolet stabilizer is used with these (SO) derivative compounds, as disclosed in U.S. Pat. No. 4,440,672, the light fatigue resistance of the (SO) dye is improved without hindering the photocolorability of the photochromic composition. Improvement of the light fatigue resistance is desirable in order to broaden the use of a photochromic article and to increase its useful lifetime.
Accordingly, it is a principal object of the present invention to provide a new class of photochromic (SO) derivative compounds which are more neutral in color after being subjected to ultraviolet light irradiation.
It is another object of the present invention to provide a new class of photochromic (SO) derivative compounds, which when incorporated into a plastic host, will produce a photochromic material with a high luminous transmittance in the unactivated state, yet which can be darkened significantly when subjected to ultraviolet light irradiation.
Yet another object is to improve the light fatigue resistance of photochromic (SO) derivative compounds of the present invention without hindering their photocolorability, by employing an ultraviolet stabilizer.
It is a further object of the present invention to incorporate such improved photochromic (SO) derivative compositions into host materials and to fabricate photochromic articles such as sunglasses, ophthalmic lenses, ski goggles, window coatings, and the like, from the resulting photochromic material.